Orthodontic bracket



April 14, 1964 P. R. BEGG 3,128,553

ORTHODONTIC BRACKET Filed Dec. 8, 1961 3 Sheets-Shget 1 April 14, 1964 P.- R. BEGG 3,128,553

ORTHODONTIC BRACKET Filed Dec- 8, 1961 3 Sheets-Sheet 2 April 14, 1964 P. R. BEGG ORTHODONTIC BRACKET 3 Sheets-Sheet 3 Filed Dec. 8, 1961 United States Patent O 3,128,553 ORTHODONTIC BRACKET Percy Raymond Begg, Shelf House, North Terrace, Adelaide, South Australia, Australia Filed Dec. 8, 1961, Ser. No. 158,093 Claims priority, application Australia Dec. 12, 1960 14 Claims. (Cl. 32-14) This invention relates to an improved orthodontic bracket assembly of the ribbon arch type usable particularly in the light arch wire technique for the correction of teeth, although the improved bracket assembly can also be used by Orthodontists who practice the rectangular arch wire technique.

When moving teeth into their correct position it is customary to attach bracket holding tooth bands to the teeth and to use an arch wire which engages these brackets in order to apply the required pressure for moving the teeth.

Under existing methods it is customary to use a square or rectangular arch wire and to have a bracket on the band which has a slot of dimension to grip the arch wire against relative rotation therewith and to allow the arch wire to exert the necessary moving or twisting force on the teeth. However, I have established that the use of excessive force in moving teeth is undesirable, and it is desirable that the force applied should be within certain close limits, the force being considerably less than that previously employed, for example, in the first stage of treatment, in the tipping of the crowns of the teeth in a mesial or distal direction, the force need only be between sixty and seventy grams. This arrangement has the dual advantage of more rapid movement of teeth as well as less discomfort to the patient.

In my light wire technique, there are usually three stages of treatment, and in their simplest form these stages may be said first to comprise tipping of the crowns of the teeth, the positions of the apices of their roots remaining relatively unaltered. The second stage has the purpose of completing the closure of extraction spaces, and again the main movement is that of tipping the crowns of the teeth.

The third stage of treatment is designed to put all of the teeth into good axial relations, that is to upright the teeth. At the third stage of treatment it is desirable to maintain the crowns of the teeth in approximately the same positions that they occupied at the end of the second stage of treatment, and to tip the roots. This of course is a very much over simplified explanation of the light arch wire technique, a fuller explanation of the technique being published in the American Journal of Orthodontics, volume 47, No. 1, pages 30 to 48, January 1961.

At the start of the light wire treatment the bracket assembly must allow the crowns of the teeth to tip freely, either mesially or distally, according to the directions which the crowns of the teeth tend to tip. The bracket during the last stage of treatment must not allow the crowns of the teeth to tip freely, but when required must be capable of exerting an active force which will move the roots of the teeth mesially or distally, the fulcrum of movement at this stage being the centre of the bracket.

Alternatively the bracket assembly in the last stage of treatment must be capable of maintaining the tooth upright so that it can be moved bodily, either mesiallyor distally as required.

The main object of this invention is to provide means which will simplify orthodonic treatment by making it possible for a single bracket to be used in the first and second stages of treatment in such a manner that the crowns of the teeth can be tipped freely, while in the third and final stage of treatment the same bracket member can have any one of a plurality of auxiliary members applied to it so that it becomes functionally a different bracket assembly which can be used either for tipping the roots of the teeth or for moving the teeth bodily, that is, moving the crowns and roots simultaneously and to the same extent. This then removes the need to change the brackets during the treatment.

It is a still further object to provide these improvements in a bracket which includes one only arch wire slot, in contrast with previously proposed brackets which employ two slots.

In its simplest form the invention may be said to consist of a bracket member the inner surface of which is weldable to a tooth band, a lock pin slot extending through the bracket member from its upper surface to its lower surface and extending outwardly from the inner surface, an arch wire retaining slot extending from side to side and downwardly from the upper surface, and an arch wire engaging auxiliary member in the bottom of the arch wire slot.

By using a wire engaging auxiliary member in the form of a pivot member which allows the crowns of the teeth to tip freely, an important advantage and new development is achieved in orthodontic treatment, while by using a wire engaging auxiliary member with outstanding wings, the effective width of the bracket can be considerably increased, and therefore the tendency for relative rotational movement mesially or distally between the bracket and the arch wire is correspondingly reduced.

By arranging the bracket member so it can retain any one of a plurality of wire engaging auxiliary members, it will be seen that in practice it is simply a matter of removing a lock from the lock pin slot in the bracket member, lifting out an auxiliary member from the arch wire retaining slot and replacing it with a further auxiliary member suitable for use in a further stage of tooth treatment, repositioning the arch wires, if necessary replacing the arch wires with other arch wires differently formed, and locking the arch wires in position with a lock pin. For example the auxiliary member to be used in the first and second stages of treatment may be the pivot member which will allow the tooth to tip firstly with its crown moving mesially or distally until it is in an upright position, and the pivot member can then be replaced with an auxiliary member with outwardly disposed wings which will prevent relative rotation mesially or distally between the tooth and the arch wire, so that the tooth can be moved bodily by the arch wire. Neither the pivot nor the other auxiliaries can be considered separately because they are complementary to each other in the successive stages of treatment.

Embodiments of the invention are described hereunder in some detail with reference to the accompanying drawings, in which:

FIG. 1 is a perspective view of an arch wire bracket assembly retaining a pair of arch wires and a pivot auxiliary member,

FIG. 2 is a fragmentary section on plane 2--222 of FIG. 1,

FIG. 3 is a perspective view of an arch wire bracket assembly containing two arch wires and a wire locking auxiliary,

FIG. 4 is a perspective view of the wire locking auxiliary used in FIG. 3, I

FIG. 5 is a perspective view similar to FIG. 3 but showing a wire locking auxiliary of slightly different form to that used in FIG. 3 and further illustrated in FIG. 4,

FIG. 6 is a rear perspective view of the Wire locking auxiliary of FIG. 5,

FIG. 7 is a perspective View of a bracket assembly containing a single arch wire and a force imparting auxiliary formed from spring wire,

FIG. 8 is a section on plane 888-8 of FIG. 7,

FIG. 9 is a view similar to FIG. 7 showing a bracket containing a single arch wire and a force imparting auxiliary formed from strip spring metal,

FIG. 10 is a view in the direction of arrow 10 of FIG. 9,

FIG. 11 is a plan view of the spring used and illustrated in FIGS. 9 and 10,

FIG. 12 illustrates a bracket member formed from pressed metal, in contrast to the brackets illustrated in FIGS. 1, 2, 3, 5, 7, 8, 9 and 10 all of which are formed from machined solid, and

FIG. 13 illustrates an auxiliary with a single outstanding wing, which can be used for the purpose of tipping a tooth.

In the following description it is assumed that the bracket and arch wires are applied or are referred to the maxillary or upper row of teeth, but quite obviously the same brackets can be inverted and used on the lower row, whereupon the upper surface becomes the lower surface and vice versa. Referring first to FIGS. 1 and 2 which show the arrangement suitable for the first and second stages of treatment, a bracket member is machined from solid stainless steel to have a pair of outstanding flanges 21, the inner surface 22 of each of which is flat and weldable to a tooth band (not shown). An arch wire retaining slot 23 is machined downwardly from the upper surface 24 and extends from one side to the other of the bracket member 29. In this embodiment the arch wire retaining slot 23 is very much deeper than the usual existing arch wire retaining slot so that it can accommodate a wire engaging auxiliary member which is in the form of a pivot member 26, two arch wires 27, and portion of the head 28 of a lock pin 29. In this embodiment the arch wires 27 are round and are of high grade austenitic stainless steel of 0.016 inch diameter, and the head of the pivot member 26 is of similar depth, so that the overall depth of the arch wire retaining slot 23 is approximately 0.050 inch, but if arch wires of different size are used, the dimensions of the bracket assembly may be changed correspondingly.

The bracket member 20 is further machined with a lock pin slot 31 which extends through the bracket member from its upper surface 24 to its lower surface 32 and outwardly from the inner surface 22, the lock pin slot being considerably deeper than the width of the arch wire retaining slot 23 so as to accommodate the lock pin 29 forwardly of the arch wires 27. The lock pin 29 is of the shape which is usually employed, the head 28 engaging the arch wires 27 and the lower end being bent over to engage the lower surface 32 of the bracket member 20.

It will be seen that the arrangement of FIGS. 1 and 2 can be used with either one or two arch wires 27, but whichever way it is used, the bracket, when welded to a band on a tooth, will permit relative rotation between the arch wires 27 and the tooth. Tins facilitates angular movement of the crown of a tooth in a mesial or distal direction.

In the third stage of treatment, it is frequently necessary to prevent any relative rotation between the bracket and the arch wire, and FIGS. 3 to 6 illustrate auxiliary members which have the effect of locking the bracket against relative rotation of the arch wire.

Referring to FIG. 3, the bracket member 20 is machined to have outstanding flanges 21, the inner surfaces 22 of which are weldable to a tooth band (not shown). An arch wire retaining slot 23 extends downwardly from the upper surface 24 of the bracket member 20. The arch wires 27 are retained in the arch wire retaining slot 23 by the head 28 of a lock pin 29 which is disposed in the lock pin slot 31, the lock pin slot 31 extending downwardly from the upper surface 24 to the lower surface 32. The wire engaging auxiliary member in this embodiment consists of the Wire locking member 34 which is machined from a solid block to have two outstanding wings 35, the upper surface of each of the wings 35 being grooved at 36 so as to retain an arch wire 27 both against relative rotation with the bracket member 20 in a mesial or distal direction and also against rotation about the vertical axis of the bracket member 20. If however rotation about the vertical axis is desired, the upper surface of the outstanding wings 35 would be flat and not grooved. The wire locking member 34 is connected between its outstanding wings by a bridge portion 38, and the wings have depending portions 39 which engage the side faces of the bracket member 20 when the bridge portion 38 is inserted in the arch wire retaining slot 23.

FIGS. 5 and 6 illustrate a slight variation of the arrangement illustrated in FIGS. 3 and 4. The bracket member 20 is of similar configuration as the bracket member in FIGS. 1 to 3 and again is formed with outstanding fianges 20, the inner surfaces 22 of which are weldable to a tooth band (not shown). The bracket member 249 is formed with an arch wire retaining slot 23 extending downwardly from the upper surface 24 and also with a lock pin slot 31 extending downwardly from the upper surface 24- to the lower surface 32, and inwardly from the inner surface 22. Arch wires 27 are retained in the arch wire retaining slot 23 by the head 28 of a lock pin 29 in the lock pin slot 31. The wire locking member ill is formed with a pair of outstanding wings 42, but the outstanding wings 42, instead of being machined with grooves as in the case of FIGS. 3 and 4, are machined with stepped landings 43, and adjacent vertical faces 44. The stepped landings 43 cooperate with the head 23 of the lock pin 25 to prevent relative rotation in a mesial or distal direction of a tooth, but the outer vertical faces 44 are in this embodiment shown machined so as to give clearance whereby a tooth can rotate about its own axis, or about a vertical axis through the bracket member 20. This arrangement has the advantage that by simply bringing the outer vertical faces 44 into alignment with the outer face of the arch wire retaining slot 23, this rotation about a vertical axis can be prevented and the arch wires 27 can be firmly engaged with said faces between the outstanding flanges 21 of the bracket member 20 and the faces 44. The wire locking member 41 engages the sides of the bracket member 20 with the depending portions 46, but in addition the depending tongue 47 also engages in the lock pin slot 31, thereby providing a backing for the lower end of the lock pin 29.

FIGS. 7 and 8 illustrate the use of a coiled wire spring 5%) as a force imparting auxiliary which is retained by the bracket member 2%. The bracket member 20 in this embodiment is substantially similar to the other embodiments, and again includes the outstanding flanges 21, the inner surfaces 22 of which are weldable to a tooth band. The arch wire retaining slot 23 extends from the upper surface 24- part-way to the lower surface 32 and from side to side of the bracket member 20. The lock pin slot 31 extends outwardly from the inner surface 22 and from the upper surface 24 to the lower surface 32 of the bracket member 20. The arch wire 27, which in this embodiment is a single instead of a pair of arch wires, is retained by the head 28 of the lock pin 29. The coiled wire spring 50 has a hook 51 at one end which engages the arch wire 27, the other end 52 of the coiled wire spring 50 passing through the lock pin slot 31 beneath the arch wire 27 and being bent over contiguous with the lower surface 32 of the bracket member 20.

The force imparting auxiliary can of course be a spring of any suitable type, and FIGS. 9, l0 and 11 show an arrangement where the coiled wire spring 50 is replaced by a flat spring 55, one end of the flat spring 55 being shaped with an arch wire engaging V-shape slot 56, while the other end 57 passes through the lock pin slot 31 of the bracket member 58, and is bent over to be contiguous with the lower surface 32 of the bracket member 58 to thereby be retained in the lock pin slot 31. The bracket member 58 in the embodiment of FIGS. 9 and 10 is of somewhat similar formation to the bracket member 30 in the previous embodiments, and the inner surfaces 22 are weldable toa tooth band (not shown). The bracket member 58 has a land 60 which together with the adjacent vertical face 61 and the outstanding flanges 21 defines an arch wire retaining slot. The lock pin 29 has a head 28, and functions and is retained in the same manner as in the previous embodiments.

FIG. 12 shows a slight variation of the bracket member 20, and illustrates a bracket member 63 which has outstanding flanges 64, the inner faces 65 of which are weldable to a tooth band. As in the case of the embodiment of FIGS. 9 and 10, the bracket member 63 has a land 66 thereon, which together with the adjacent vertical faces 67, and the outstanding flanges 64 define an arch wire retaining slot. The bracket member 63 however is formed from sheet metal and its two sides 63 are spaced apart to thereby form the lock pin slot 31.

FIG. 13 illustrates an auxiliary with a single outstanding wing 70 which is channelled at 71 to engage the under surface of an arch Wire at one side of a bracket member. The depending tongue 72 is shaped to engage in a lock pin slot inwardly of a lock pin, while the buttress 73 terminates in a vertical surface 74 engageable against the outside face of a bracket member.

A consideration of all the above embodiments will indicate that all the arch wire engaging auxiliary members are disposed beneath the arch wires. This arrangement has a number of advantages, firstly in that it allows an ordinary standard lock pin to be used, secondly that the auxiliaries are conveniently placed beneath the arch wires and thereby do not interfere with the intermaxillary hooks which are placed on the gingival side of the arch wire, and thirdly that the auxiliaries are disposed on the opposite side of the main arch wire to the auxiliary arch wire which has formed spurs, that is placed in the brackets gingivally to the main arch wire. For example, in the treatment of the third stage, the auxiliaries are first placed in the bracket, then the main arch wire is placed in the bracket, the main arch wire being formed with its intermaxillary hook pointing up gingivally, then at the uppermost part of the arch wire retaining slot the auxiliary arch wire which contains vertical root torqueing spurs is positioned in the bracket, the entire assembly being retained by the single lock pin.

What I claim is:

1. An improved orthodontic bracket assembly comprising a bracket member the inner surface of which is weldable to a tooth band, a lock pin slot extending through the bracket member from its upper surface to its lower surface and extending outwardly from the inner surface, an arch wire retaining slot extending from side to side and downwardly from the upper surface, and an arch wire engaging auxiliary member in the base of the arch wire slot.

2. An improved orthodontic bracket assembly comprising a bracket member the inner surface of which is weldable to a tooth band, a lock pin slot extending through the bracket member from its upper surface to its lower surface and extending outwardly from the inner surface, an arch'wire retaining slot intersecting the lock pin slot and extending from side to side and downwardly from the upper surface, and an arch wire engaging auxiliary member in the base of the arch wire slot, a portion of the arch wire auxiliary member engaging in the lock pin slot beneath the bottom of the arch wire slot.

3. An improved orthodontic bracket assembly comprising a bracket member the inner surface of which is weldable to a tooth band, a lock pin slot extending through the bracket member from its upper surface to its lower surface and extending outwardly from the inner surface, an arch wire retaining slot extending from side to side and downwardly from the upper surface, an arch wire engaging auxiliary member in the base of the arch wire slot, a portion of the arch wire auxiliary member engaging in the lock pin slot beneath the bottom of the arch wire slot, and a lock pin in the lock pin slot disposed forwardly of the arch wire auxiliary member.

4. An improved orthodontic bracket assembly comprising a bracket member, outstanding flanges on the inner end of the bracket member, the inner surface of each of the outstanding flanges being weldable to 'a tooth band, a lock pin slot extending through the bracket member from its upper surface to its lower surface and extending outwardly from said inner surfaces, an arch wire retaining slot extending from side to side and downwardly from the upper surface, an arch wire engaging auxiliary member in the base of the arch wire slot and a lock pin in the lock pin slot, disposed forwardly of the arch wire auxiliary member.

5. An improved orthodontic bracket assembly comprising a bracket member, outstanding flanges on the inner end of the bracket member, the inner surface of each of the outstanding flanges being weldable to a tooth band, a lock pin slot extending through the bracket member from its upper surface to its lower surface and extending outwardly from said inner surfaces, an arch wire retaining slot extending from side to side and downwardly from the upper surface, a pivot member in the base of the arch wire slot engageable against the under surface of an arch wire slot engageable against the under surface of an arch wire when disposed in the arch wire slot above the pivot member, and a lock pin in the lock pin slot and disposed forwardly of the pivotmember, the head of the lock pin being adapted to retain an arch Wire and the pivot member in the arch wire slot.

6. An improved orthodontic bracket assembly comprising a bracket member, outstanding flanges on the inner end of the bracket member, the inner surface of each of the outstanding flanges being weldable to a tooth band, a lock pin slot extending through the bracket member from its upper surface to its lower surface and extending outwardly from said inner surfaces, an arch wire retaining slot extending from side to side and downwardly from the upper surface to a depth of at least 0.040 inch, a pivot member in the base of the arch wire slot for engaging the under surface of an arch wire disposed in the arch wire slot above the pivot member, and a lock pin in the lock pin slot and disposed forwardly of the pivot member, the head of the lock pin adapted to retain an arch wire and the pivot member in the arch wire slot.

7. An improved orthodontic bracket assembly comprising a bracket mmeber, outstanding flanges on the inner end of the bracket member, the inner surface of each of the outstanding flanges being weldable to a tooth band, a lock pin slot extending through the bracket memher from its upper surface to its lower surface and extending outwardly from said inner surfaces, an arch wire retaining slot intersecting said lock pin slot and extending from. side to side and downwardly from the upper surface to a depth. of at least 0.040 inch, the front faces of said outstanding flanges being aligned with the rear face of said arch wire slot, an arch wire engaging auxiliary member in the base of the arch wire slot, and a lock pin in the lock pin slot disposed forwardly of said auxiliary member.

8. An improved orthodontic bracket assembly comprising a bracket member, outstanding flanges on the inner end of the bracket member, the inner surface of each of the outstanding flanges being weldable to a tooth band, a lock pin slot extending through the bracket member from its upper surface to its lower surface and extending outwardly from said inner surfaces, an arch wire retaining slot extending from side to side and downwardly from the upper surface to a depth of at least 0.040 inch, a Wire locking member including an outstanding wing and a depending tongue disposed in the base of the arch wire retaining slot with said tongue depending into the lock pin slot and said outstanding wing extending outwardly from said bracket member.

9. An improved orthodontic bracket assembly comprising a bracket member, outstanding flanges on the inner end of the bracket member, the inner surface of each of the outstanding flanges being weldable to a tooth band, a lock pin slot extending through the bracket member from its upper surface to its lower surface and extending outwardly from said inner surfaces, an arch wire retaining slot extending from side to side and downwardly from the upper surface to a depth of at least 0.040 inch, a wire locking member including a pair of outstanding wings interconnected by a bridge portion, a tongue depending centrally from the bridge portion, said bridge portion disposed in the base of the arch wire retaining slot with said tongue depending into the lock pin slot, said outstanding wings contiguous with the outer side surfaces of said bracket member, the shape of the upper surfaces of said outstanding wings including grooves.

10. An improved orthodontic bracket assembly comprising a bracket member, outstanding flanges on the inner end of the bracket member, the inner surface of each of the outstanding flanges being weldable to a tooth band, a lock pin slot extending through the bracket member from its upper surface to its lower surface and extending outwardly from said inner surfaces, an arch wire retaining slot extending from side to side and downwardly from the upper surface to a depth of at least 0.040 inch, a wire locking member including at least one outstanding wing and a depending tongue disposed in the base of the arch wire retaining slot with said tongue depending into the lock pin slot and said outstanding wing or wings extending outwardly from said bracket member, the shape of the upper surfaces of said outstanding wing or Wings including grooves, a main arch wire in the arch wire slot and engaging said grooves, an auxiliary arch wire in the arch wire slot and contiguous with the main arch wire, a lock pin in the lock pin slot, the head of the lock pin retaining both arch wires and the wire locking member in the arch wire slot.

11. An improved orthodontic bracket assembly comprising a bracket member, outstanding flanges on the inner end of the bracket member, the inner surface of each of the outstanding flanges being weldable to a tooth band, a lock pin slot extending through the bracket member from its upper surface to its lower surface and extending outwardly from said inner surfaces, an arch wire retaining slot extending from side to side and downwardly from the upper surface to a depth of at least 0.040 inch, an arch wire in the arch wire slot, a spring, a hook on one end of the spring engaging the under surface of the arch wire to one side of the bracket member, a plurality of coils in the spring adjacent a side surface of the bracket member, the other end of the spring engaged in the lock pin slot beneath the arch wire, and a lock pin in the lock pin slot, the head of the lock pin retaining the arch wire in the arch wire slot and said other end of the spring in the lock pin slot, whereby the spring imparts a force urging relative rotation between said bracket member and said arch wire.

12. An improved orthodontic bracket assembly comprising a bracket member, outstanding flanges on the inner end of the bracket member, the inner surface of each of the outstanding flanges being weldable to a tooth band, a lock pin slot extending through the bracket member from its upper surface to its lower surface and extending outwardly from said inner surfaces, an arch wire retaining slot extending from side to side and downwardly from the upper surface to a depth of at least 0.040 inch, a spring member, one end of the spring member extending outwardly from said bracket member and being engageable beneath an arch wire when said arch wire is secured in said bracket member, the other end of the spring member being engaged in the lock pin slot, and a lock pin in the lock pin slot disposed forwardly of said spring member, whereby the spring member is operable to impart a force urging relative rotation between said bracket member and said arch wire.

13. An improved orthodontic bracket assembly comprising a bracket member, outstanding flanges on the inner end of the bracket member, the inner surface of each of the outstanding flanges being weldable to a tooth band, a lock pin slot extending through the bracket member from its upper surface to its lower surface and extending outwardly from said inner surfaces, an arch wire retaining slot extending from side to side and downwardly from the upper surface to a depth of at least 0.040 inch, an arch wire in the arch wire slot, a spring, a hook on one end of the spring engaging the under surface of the arch wire to one side of the bracket member, a plurality of coils in the spring adjacent a side surface of the bracket member, the other end of the spring engaged in the lock pin slot beneath the arch wire, and a lock pin in the lock pin slot disposed forwardly of said other end of the spring, the head of the lock pin retaining the arch wire in the arch wire slot and said other end of the spring in the lock pin slot, whereby the spring imparts a force urging relative rotation between said bracket member and said arch wire.

14. An improved orthodontic bracket assembly comprising a bracket member, outstanding flanges on the inner end of the bracket member, the inner surface of each of the outstanding flanges being weldable to a tooth band, a lock pin slot extending through the bracket member from its upper surface to its lower surface and extending outwardly from said inner surfaces, an arch wire retaining slot extending from side to side and downwardly from the upper surface to a depth of at least 0.040 inch, an arch wire in the arch wire slot, a flat spring, one end of the spring engaging the under surface of the arch wire to one side of the bracket member, the other end of the spring engaged in the lock pin slot beneath the arch wire, and a lock pin in the lock pin slot disposed forwardly of said other end of the spring, the head of the lock pin retaining the arch wire in the arch wire slot and said other end of the spring in the lock pin slot, whereby the spring imparts a force urging relative rotation between said bracket member and said arch wire.

References Cited in the file of this patent UNITED STATES PATENTS 1,821,171 Atkinson Sept. 1, 1931 

1. AN IMPROVED ORTHODONTIC BRACKET ASSEMBLY COMPRISING A BRACKET MEMBER THE INNER SURFACE OF WHICH IS WELDABLE TO A TOOTH BAND, A LOCK PIN SLOT EXTENDING THROUGH THE BRACKET MEMBER FROM ITS UPPER SURFACE TO ITS LOWER SURFACE AND EXTENDING OUTWARDLY FROM THE INNER SURFACE, AN ARCH WIRE RETAINING SLOT EXTENDING FROM SIDE TO SIDE AND DOWNWARDLY FROM THE UPPER SURFACE, AND AN ARCH WIRE ENGAGING AUXILIARY MEMBER IN THE BASE OF THE ARCH WIRE SLOT. 